Speed control apparatus

ABSTRACT

At the delivery end of a sheeter, the cut sheets are taken from a conveyor and propelled by final rolls onto a stack. The final rolls must rotate at or above a minimum speed, while the conveyor can go below this. Normally the two speeds are related. The conveyor speed is monitored and for normal running the final rolls are governed by the monitor signal. For low conveyor speeds, this is cut out electronically and a constant governing signal applied instead to cause the final rolls to maintain a minimum speed.

United States Patent on Bossons Sept. 23, 1975 l l SPEED CONTROL APPARATUS [75] Inventor: Walter Howard Bossons Almondsbury, England [73] Assignce: Masson Scott Thrissell Engineering Limited, Bristol. England [22] Filed: Apr. 1, 1974 [21] Appl. No.: 456,451

[30] Foreign Application Priority Data Apr. 3. I973 United Kingdom 158i H73 [52] U.S. Cl .i 271/69; 198/76 [5|] lnt Cl. .t B65H 29/16; B65H 29/22 [58] Field of Search ,4 271/69, 202, 203; 198/76 [56] References Cited UNITED STATES PATENTS 3.527.460 9/1970 Lopez 27l/69 3.542.362 ll/l970 Broekmuller ct alv 27l/202 Primary Etuminen-Evon C. Blunk Asxistml! Examiner-Bruce H. Stoner. Jr Allflrfkl" Agerm 0r FirmYoung & Thompson [57] ABSTRACT At the delivery end of a sheeter. the cut sheets are taken from a conveyor and propelled by final rolls onto a stack The final rolls must rotate at or above a minimum speed. while the conveyor can go below this. Normally the two speeds are related The conveyor speed is monitored and for normal running the final rolls are governed by the monitor signal. For low conveyor speeds. this is cut out electronically and a constant governing signal applied instead to cause the final rolls to maintain a minimum speed.

9 Claims, 8 Drawing Figures US Patent Sept. 23,1975 shw 2 on 3,907,275

FINAL ROLL DRIVE F7T/M/N.

20fi 60X 100 2b0 300 SECONDARY CONVEYOR F T/M/N US Patent Sept. 23,1975 Sheet 3 of4 3,907,275

FIG. 4.

Sheet 4 of 4 Fla. 7.

SPEED CONTROL APPARATUS This invention relates to web cutting machines and is particularly concerned with the cutting and stacking of sheets of paper or board.

The final roll of a sheeter receives the sheets that have just been cut by a rotary knife or knives and projects them onto a stack. The sheets are normally moved from the knives to the final roll via a primary conveyor and a secondary conveyor. The final roll is set to a speed appropriate to the size of sheet, the feed speed of the continuous web to the knives and the rate at which the knives are cutting. It will be appreciated that there is a certain minimum speed at which the final roll can project the cut sheets over the stack to contact the layboy backboard and settle on the growing stack of paper in a satisfactory manner. The secondary eonveyor may be running more slowly than this, and at such slower speeds the drive for the final roll should be independent and at least at said minimum. Above the critical minimum speed the final roll should rotate at a speed substantially corresponding to the delivery speed of the sheets from the conveyor, although it may be desirable to allow the final roll to be adjustable within limits either side of the conveyor speed.

It has been proposed in our earlier US. Pat. No. 1,317,884 .to solve this problem by a mechanical drive with a positive infinitely variable (PIV) gear box setting the ratio between the final roll and the secondary conveyor and with a free wheel system to ensure maintenance of the minimum final roll speed. There is a main motor for normal running, when the gear box is operative, while the drive of the final roll at the minimum speed is taken from a geared motor which also powers the staekingjogger. The free wheel arrangement effects the change-over automatically. The necessary adjustment of the controls was originally made on the apparatus itself but this was inconvenient in operation. The controls have latterly been remotely operated by pilot motors but this makes the system even more complex and expensive.

It is an object of this invention to provide sheet feeding mechanism with speed controls of considerably simplified form.

According to the present invention there is provided sheet feeding mechanism for web cutting machines including a conveyor for cut sheets, delivery means at the downstream end of the conveyor for receiving the sheets and delivering them to a layboy or the like, drive means for the conveyor and for the delivery means, and means for controlling the speed of the delivery means in accordance with the speed of the conveyor comprising means for producing a signal related to the speed of said conveyor, means for applying said signal as a control output to the drive means for the delivery means, thereby to drive the latter at a speed related to that of the conveyor, and over-ride means for rendering said applying means ineffective for signals indicating speeds below a limiting speed and to apply instead a constant control output.

Preferably said over-ride means is adjustable to give different selected limiting speeds. In a preferred embodiment there are means for biasing said signal to produce a modified control output representing a speed different from that of said conveyor. These biasing means may also be adjustable. and so enable the deliw ery means to run at speeds greater, equal to or less than the speed of said conveyor.

There may be separate motors for the delivery means and the secondary conveyor, or a single motor may be arranged to drive the conveyor means and the delivery means. one through a variable transmission and the other directly.

In one preferred arrangement the drive means for the delivery means is a DC. motor with a constantly energised field and an armature current controlled in accor dance with said output. This output may operate through a phase angle controlled rectifier.

The invention may be performed in various ways and one constructional form will now be described. by way of example, with reference to the accompanying drawings, in which:

FIG. I is a diagram of a secondary conveyor and final roll with separate drive means and speed control apparatus according to the invention,

FIG. 2 is a graph illustrating the relationship between the speeds of the conveyor and the final roll,

FIG. 2a is a graph showing a typical relationship between the speed of the final roll and the speed of the secondary conveyor,

FIG. 3 is a circuit diagram of a comparator.

FIG. 4 is a schematic diagram of a phase angle controlled rectifier motor drive,

FIG. 5 is a schematic diagram of a variable coupling controller, and

FIGS. 6 and 7 are diagrams of alternative drive arrangements for secondary conveyors and final rolls.

In FIG. 1, the secondary conveyor 1 has independent drive means 1A but the speed of rotation of the drive roller is indicated by a tachometer 2, and this corre sponds to the delivery speed of the sheets S of cut paper or board. The final roll 3 is driven by a motor 4 the speed of which is governed from a control circuit 5 which has as its inputs both the speed of the secondary conveyor and two parameters from an operators panel 6 as will be described in more detail below. There is also a feedback of the speed of the final roll 3 from an associated tachometer 7. The sheets will be stacked on a layboy indicated in outline at 8, and this will normally be equipped with backboard joggers driven by a separate A.C. constant speed motor (not shown).

Referring to FIG. 2 the ordinates represent the final roll drive speed in feet per minute (this will be the circumferential speed of the roll) and the abscissae the secondary conveyor speed. The continuous line through the origin represents identical conveyor and final roll drive speeds. As stated above, it is desirable that the final roll speed should be adjustable either side of this secondary conveyor speed and the parallel inclined broken lines represent the limits of the desirable adjustment. Also, while the secondary conveyor may run at any speed the final roll must have a minimum speed, and with the circuit described below this minimum may be set to any value within a given range, such a range being indicated by the broken lines parallel to the horizontal axis.

FIG. (20) indicates a typical operating curve for the final roll drive. where the secondary conveyor speed is followed with a positive 5 percent differential until the speed of feet per minute is reached. The final roll will thereafter maintain this minimum speed.

Referring now to FIG. 3, this shows a circuit diagram of a comparator which serves as a speed tracking circuit giving an output that is related to the speed of the secondary conveyor as sensed by the tachometer 2. This tachometer input is applied to the terminal 11 through a resistance [2 to an operational amplifier I3. A potentiometer l4 biasses this input according to the setting of its tap. At a central position it has no effect, towards the positive end and it will modify the input to give the effect of a greater secondary conveyor speed and towards the negative end the effect of a lesser speed. Its range corresponds to the band width between the inclined broken lines of FIG. 2. The operational amplifier 13 has feedback through a resistor 15 and. sometimes, through a diode 16, the latter being in a line from the tap of a potentiometer I7 which serves as means for setting the minimum speedv Given a particular setting of the potentiometer 17, when the effective input to the amplifier is sufficient to keep the diode l6 non-conducting the amplifier 13 functions normally to give a control output from terminal 18 that is in accordance with the input. In other words the control output. which governs the speed of the final roll, tracks the secondary conveyor speed, to a greater, equal or lesser extent depending on the setting of potentiometer 14. When the effective input speed falls below the critical limiting speed, the diode 16 conducts and the gain of the amplifier l3 falls to zero. The control output is then constant and will maintain the final roll at a given minimum speed depending on the setting of potentiometer I7. The range of potentiometer 17 corresponds to the band width between the horizontal broken lines of FIG. 2.

The potentiometers and their control knobs will be on the operator's panel 6, and this will also have dials indicating the two speeds.

The control output from the circuit of FIG. 3 can be used in many ways to govern the speed of the motor 4, which drives the final roll 3. In one preferred form the motor 4 is a DC. variable speed motor and the control output from terminal 18 is applied through the circuit shown in FIG. 4. The motor has a constantly energised field. the field winding 19 being connected across a fixed rectifier 20, while the armature current is varied in response to the signal applied at terminal 18.

This signal passes through two amplifying stages 21 and 22 and thence to a pulse width modulator 23. There is an A.C. supply (not shown) and a ramp voltage is generated in synchronism with the A.C. halfcycles and applied to the reference of a comparator circuit. The control signal is applied to the input of the comparator, and a pulse is obtained when comparison is reached. This is differentiated and applied as the firing or triggering pulse to a controlled rectifier 24, which receives the A.C. supply. The rectifier will conduct for the remainder of the A.C. half-cycle, being blocked over the phase angle between the supply A.C. zero point and the generation of a firing pulse.

The circuit also has stabilising loops 25 and 26 feed ing back signals which are functions of the armature voltage and current to the amplifying stages 21 and 22. These are adjusted by the potentiometers to give the required response, and will give generally stable operation. It may be preferred for very accurate speed holding, however. to apply to alternative feedback input 27, indicated in outline, a tachometer-derived signal corresponding to the speed of the motor 4.

Instead of having separate drive means for the secondary conveyor and the final roll, a single motor can be employed to drive either the secondary conveyor or the final roll directly and the final roll or the secondary conveyor through an electrically controlled variable coupling. This may be a hydraulic unit. a magnetic coupling or an eddy current coupling. such as a TASC" unit, combined with fixed ratio gearing to achieve the desired speeds and speed ratios.

The variable coupling control circuit, referring to FIG. 5, will be supplied with a signal at terminal I8 corresponding to the desired speed. This signal is compared with a speed signal at terminal 27 from a tachom eter. The resulting error signal is amplified in amplifier 28, shaped by pulse width modulator 29, and used to control a controlled rectifier or power stage 30 ene rgising the variable coupling 31. The output speed of this coupling may be adjusted as in the previous example.

FIG. 6 is a diagram of a secondary conveyor and final roll with a single motor drive where the motor 4 drives the final roll 3 directly and the secondary conveyor 1 through a variable magnetic coupling 32.

FIG. 7 is a diagram of a secondary conveyor 1 and final roll 3 with a single motor drive where the motor 4 drives the secondary conveyor 1 directly and the final roll 3 through a variable hydraulic coupling 32.

The components are otherwise similarly referenced to FIG. 1, and it will be understood that directly' includes fixed gears in the drive.

It will be understood that the speed of the secondary conveyor will be controlled in accordance with the speed of the earlier stages of the sheeter. That may be achieved in ways not forming part of the present invention, which is concerned with the relationship between the secondary conveyor and the final roll.

I claim:

1. Sheet feeding mechanism for web cutting machines including a conveyor for cut sheets. delivery means at the downstream end of the conveyor for receiving the sheets and delivering them to a layboy or the like. drive means for the conveyor and for the delivery means, and means for controlling the speed of the delivery means in accordance with the speed of the conveyor comprising means for producing a signal related to the speed of said conveyor, means for applying said signal as a control output to the drive means for the delivery means, thereby to drive the latter at a speed related to that of the conveyor, means for biasing said signal to produce a modified control output representing a speed different from that of said conveyor. and over-ride means for rendering said applying means ineffective for signals indicating speeds below a limiting speed and to apply instead a constant control output.

2. A mechanism as claimed in claim I, wherein said over-ride means is adjustable to give different, selected limiting speeds.

3. A mechanism as claimed in claim 1, wherein said biasing means is adjustable.

4. A mechanism as claimed in claim 3, wherein said biasing means enables the delivery means to run at speeds greater. equal to or less than the speed of said conveyor.

5. A mechanism as claimed in claim 1. wherein there are separate motors for the conveyor and the delivery means.

6. A mechanism as claimed in claim I, wherein the drive means is a single drive motor and a variable transmission device, the motor driving one of the conveyor 9. A mechanism as claimed in claim I. wherein the drive means for the delivery means is a DC motor with a constantly energised field and an armature current controlled in accordance with said output. 

1. Sheet feeding mechanism for web cutting machines including a conveyor for cut sheets, delivery means at the downstream end of the conveyor for receiving the sheets and delivering them to a layboy or the like, drive means for the conveyor and for the delivery means, and means for controlling the speed of the delivery means in accordance with the speed of the conveyor comprising means for producing a signal related to the speed of said conveyor, means for applying said signal as a control output to the drive means for the delivery means, thereby to drive the latter at a speed related to that of the conveyor, means for biasing said signal to produce a modified control output representing a speed different from that of said conveyor, and over-ride means for rendering said applying means ineffective for signals indicating speeds below a limiting speed and to apply instead a constant control output.
 2. A mechanism as claimed in claim 1, wherein said over-ride means is adjustable to give different, selected limiting speeds.
 3. A mechanism as claimed in claim 1, wherein said biasing means is adjustable.
 4. A mechanism as claimed in claim 3, wherein said biasing means enables the delivery means to run at speeds greater, equal to or less than the speed of said conveyor.
 5. A mechanism as claimed in claim 1, wherein there are separate motors for the conveyor and the delivery means.
 6. A mechanism as claimed in claim 1, wherein the drive means is a single drive motor and a variable transmission device, the motor driving one of the conveyor means and the delivery means directly and the other through said variable transmission device.
 7. A mechanism as claimed in claim 6, wherein the variable transmission device is a magnetic coupling.
 8. A mechanism as claimed in claim 6, wherein the variable transmission device is a hydraulic coupling.
 9. A mechanism as claimed in claim 1, wherein the drive means for the delivery means is a D.C. motor with a constantly energised field and an armature current controlled in accordance with said output. 